Process of making chromates.



W. T. GIBBS. PROCESS OF MAKING GHROMATES.

APPLICATION FILED snmazo, 1907.

S 901,436. v v I Patented 0ct. 20,1 908.

WA J mg/V are roasted while the interiors remain'unmosphere into t UNITED STATES P gan OFFICE.

WILLIAM T. GIBBS, OFv BUGKINGHAM,

QUEBEC, CANADA, ASSIGNOR TO THE NATIONAL ELECTROLYTIC COMPANY, A CORPORATION OF NEW YORK.

raocnss or MAKING GHROHATES.

Specification of Letters Patent.

' Patented Oct. 20, 1908.

To all whom it may concern: 7

-Be it known that I, WILLIAM TAYLOR Gmns, a subject of the King of Great Britain and Canada, residing at Buckingham, Province of Quebec, county of Ottawa-Canada, have invented certain new and useful I1nprovements in Processes of Maki Chromate of Soda and other Chromates, fullydescribed and represented in the following specification.

This invention relates especially to a new method of making chromate of sodafrom chrome iron ore, but the method is applicable also toother chromates; 7

The manufacture of chromate of soda is at present usually carried out by roasting a mixture of finely ground chrome .iron ore, lime, and carbonate of soda at a high tern erature on the hearth of a reverberatory nace. The labor cost of this process-is very high and a considerable amount of chrome ore is unacted upon and lost. 'Attempts have been made to carry out this process in mechanicall ut the results secured ave beenunsatisfactory, owing to the material for into solid lumps or masses, the surfaces of which changed.

I have discovered that by using a mixture of finely ground chrome iron ore and sufiicient carbonate of soda -to give a fluid melt out the process in a rotary at the heavy ore is constantly and falls. throu h the heated oxidizing atdie bath of molten alkali in the bottom of the furnace, the material does not form-into solid lumps or masses and the oreis completely decomposed and the lime used in the hearth process may be entirely omitted. The-process results .also in the production andpossible recovery of aluminate of soda, so that a process of simultaneously roducing aluminates and chromatesu,

is provi ed. The process is applicable also with other chromates as, for instance, with carbonate of potassium to produce chromate of otassium. I

rotating furnace kept at a'proper tempera:

operated furnaces,

c 11 carrying out my process in the pres ferred manner to produce chromate of soda,

ture, The, amount of carbonate of soda and the furnace temperature may be varied somewhat so long as they are sufficient to keep the mass fluid, and will vary under different conditions, but I have secured satisfactory results with the carbonate of soda about one and twothirds times the weight of'the chrome iron ore, and with furnace tem eratures of about 1200 centigradc.

T e reaction commences at once and, by the rotating of the furnace, constantly agitated and mixed, and the ore, which sinks to the bottom of the bath of 'molten alkali, is continuously carried up and dropped through the heated oxidizing atmosphere within the furnace into the bath, so as to be continuously exposed to heat and oxygen and the solvent action of the bath of fused alkali. Even when. under the bath, moreover, the ore is at a high temperature,

as every part of the rotary furnace wall is exposed to the full heat, and that portion of the furnace which is temporarily under the bath is approximately as hot as other portions and is not protected from the heat as it would be in an ordina reverberatory furnace. The ore is comp etely decomposed in a few hours, the whole of the chromium oxid of the ore being converted into chrornic trioxid. The fluid mass is then run out of the furnace, allowed to cool, crushed to about one quarter inch pieces and agitated with water. The chromate of soda is uickly dissolved together with the excess 0 carbonate of soda and some aluminate of soda which is formed by the action of the soda on the alumina of the ore. I The solutionis filtered from the insoluble residue, and the alumina and carbonate of soda thenremoved by any well-known or suitable method and the remaining chromate of soda solution then treated in any desired manner.

' The process is very efiicient and economical, I

and as compared with the lime process secures the important advantages, in addition to the great saving of labor, that it avoids the loss of chrome ore incident to the lime process, and the residues insoluble in water and the alumina recovered from the solution both have commercial values, whereas the residue from the lime process is waste material.

In the accompanying drawing there is shown diagrammatically a rotary furnace suitable for carrying out the present invention.

' acted upon by the charge, such for instance as magnesite brick, the ordinary level of the charge being indicated by the line X. This furnace is s own as fired by gas introduced through gas pipe B, the air sup ly through opening 11 around the gas pipe eing in excess of that required for the complete combustion of the gas, so as to maintain the oxidizing atmosphere desired in the furnace,

and the other end of the furnace being connected with a stack 0 controlled by a damper 12, to prpvide a draft which may be regulated as desired. It will be understood, however, that the construction of the furnace, and means for firing it and securing the oxidizing atmosphere, may be varied.

What I claim is v 1. In a process of making chromates, roast ing finely ground chrome iron ore mixed with sufficient alkaline carbonate and at a sufficient temperature to keep the mass fluid and continuously raising the ore from the fluid mass and returning it to the bath to subject it to the oxidizing atmosphere above the bath.

2. In a process of makin chromate of soda, roasting finely ground cirome iron ore mixed with sufiicient carbonate of soda and at. sufficient temperature to keep the. mass fluid, and rotating vertically the furnace chamber containing the ore during the roast-' mg process.

3. The process of simultaneously producing aluminates and chromates, which con- I sists. in roasting finel ground chrome iron ore, mixed with sufficient alkaline carbonate and at a sufficient temperature to keep the mass fluid and rotating vertically the furnace chamber containing the ore during the roast mg process, and dissolving out the aluminate and chromate.

4. The process of simultaneously producing aluminate and chromate of soda, which consists in roastingl suitable material un-' air, and dissolving out finely ground chrome iron ore mixed wit sufficient carbonate of soda and at a sufficient temperature to keep the mass fluid and rotating vertically the furnace chamber containing the ore during the roasting process, and dissolvingout the aluminate and chromate of soda.

5. In a process for making chromates, roasting finely ground chrome iron ore mixed with sufficient alkaline carbonate and at a sufficient temperature to keep the mass fluid, and agitating said fused mixture while exposin the'same to the action of air.

6. n a process of makin chromate of soda, roasting finely ground 0 ome iron ore mixed with sufficient carbonate of soda at a sufficient temperature to keep the mass fluid, and agitating said fused mixture while exposing the same to the action of air.

7. The process of simultaneously producing ialuminates and chromates, which consists in roastingfinel ground chrome iron ore, mixed with sufficient alkaline carbonate and .at a sufficient temperature mass,.fluid and agitating said fused mixture while exposing the same to the action of air, and dissolving out the aluminate and chromate.

, 8. The process of simultaneously producing aluminate and chromate of soda, whlch consists in roastin finely ground" chrome iron ore mixed with sufficient carbonate of soda and at a sufficient temperature to keep the mass fluid and a tating said fused mixture while exposing t iie same to the action of the aluminate and chromate of soda.

In testimon whereof, I have hereunto set my hand, in t 0 presence of two subscribing witnesses.

' WHJLIAM T. GIBBS.

Witnessesi HORACE M. SANFORD,

WALTER A. WILLIAMS.

to keep the 

